This invention relates to an improved method and apparatus for analyzing leaks caused by faults in hollow structures.
In the past, hoses and the like such as those made from polypropylene were tested by submerging a pressurized hose into a tank of water and then visually inspecting for air bubbles. This method was found to be undesirable because of the time involved, and the lack of accurate and objective testing resulting therefrom. Thus, in many instances, the hoses were installed in mechanisms such as for example, washing machines, wherein a fault in a hose would not normally be detected until a final quality control inspection. Thus, the replacement of faulty hoses involved excessive disassembly time of the washing machine and increased production costs to the customers. In view of this, there has arisen a requirement that each and every hose manufactured be tested before the hose is installed in a piece of equipment. In the aforementioned manual testing method, approximately seven inches at each end of the hose extended out of the water during the test resulting in 15 to 20% of each hose not being inspected. Further, air bubbles adhering to the outer wall of the hose and the turbulence of the water made visual inspection of leakages very difficult. In addition, very small holes such as holes less than 0.008 inch were very difficult to detect because of the speed with which the test had to be conducted if the manufacture of the hoses on an assembly line basis was to be at all economically feasible.
Another drawback to manual water testing was that such testing necessitated multiple handling operations and additional personnel to achieve the necessary production requirements. Thus, for example, the production and testing of hoses entailed the assembly of a hose section and often times the assembly and welding or bonding of two hose sections together to make a hose of sufficient length, placing the completed hose into a relatively large container, leakage testing the hose, replacing any faulty hose and then packaging the good hoses. A secondary problem resulted in the fact that cardboard shipping containers are generally desired because of economic factors relating thereto. However, since the hoses were water tested, water remaining in the hoses after testing had a tendency to damage the cardboard shipping containers. In addition, health and safety standards have presented a problem because of water spillage around the leakage test work area.
In view of the aforementioned problems with manual testing of hoses on a mass production basis, efforts have been made to develop a testing apparatus for testing hoses on a mass production basis. In one such development effort, each end of the hose was plugged and compressed air was then introduced through one of the plugs in the hose. The pressure was increased to a preset level at which point the introduction of compressed air into the hose was terminated. Then after a predetermined period of time the pressure within the hose was sampled. This testing method created a problem in that the hose, particularly when thin hoses were tested, resulted in a ballooning or expanding of the pressurized hose resulting in a significant volume variation within the hose and a corresponding internal pressure change. Thus, it was found that pressurizing the internal volume of a hose and then detecting the pressure drop therein resulted in test results which varied widely, particularly in the case of thin hoses which had a tendency to expand or balloon under the pressurized air which expansion resulted in a lack of precision in measuring the integrity of the hoses.
It accordingly is an object of this invention to provide a method and apparatus for accurately detecting faults in hollow structures.
It is another object of this invention to provide an automatic means for detecting faults in hollow structures accurately and efficiently.